ES3024089T3 - Process for the purification of hydrogen peroxide - Google Patents

Abstract

The present invention relates to a novel process configuration for the purification of an aqueous hydrogen peroxide (H2O2) solution containing organic impurities. (Automatic translation with Google Translate, no legal value)

Description

DESCRIPTION

Procedure for the purification of hydrogen peroxide

This application claims priority filed on December 22, 2022, in Europe under number 22216112.7.

TECHNICAL FIELD

The present invention relates to a new process configuration for the purification of an aqueous solution of hydrogen peroxide (H<2>O<2>) containing organic impurities.

TECHNICAL BACKGROUND

Hydrogen peroxide is one of the most important inorganic chemicals produced worldwide. Its industrial applications include bleaching of fabrics, pulp, and paper, organic synthesis (propylene oxide, caprolactam), the manufacture of inorganic chemicals and detergents, environmental applications, and others.

Hydrogen peroxide synthesis is predominantly achieved by the Riedl-Pfleiderer process (originally described in U.S. Patent Nos. 2,158,525 and 2,215,883), also called the anthraquinone loop process or AO (autoxidation) process.

The well-known process is a cyclic procedure that takes an organic anthraquinone dissolved in a solvent and circulates this “Working Solution - WS” mixture around the plant.

The first step of the AO process is the chemical reduction of two main organic species (useful quinone(s)) (2-alkylanthracene-9,10-dione and/or 6-alkyl-1,2,3,4-tetrahydroanthracene-9,10-dione) to the corresponding hydroquinone(s) (2-alkylanthracene-9,10-diol and/or 6-alkyl-1,2,3,4-tetrahydroanthracene-9,10-diol) using hydrogen gas and a catalyst. The mixture of organic solvents, hydroquinone species and quinone is then separated from the catalyst, and the hydroquinone species are oxidized using oxygen, air or oxygen-enriched air, thereby regenerating the quinone(s) with the simultaneous formation of hydrogen peroxide.

The organic solvent is typically a mixture of two solvents, one a good solvent for dissolving the quinone(s) (usually a non-polar solvent, e.g. a mixture of aromatic compounds), and the other a good solvent for dissolving the hydroquinone(s) (usually a polar solvent, e.g. a long-chain alcohol). The hydrogen peroxide is then typically stripped in an extraction column with water, recovered as a crude aqueous hydrogen peroxide solution, and the working solution is returned to the hydrogenator to complete the cycle. Therefore, the typical layout of a standard hydrogen peroxide plant can be summarized as starting with a hydrogenator, followed by an oxidation column, followed by an extraction column. The hydrogen peroxide is usually stripped from the working solution into a stream of demineralized water from the extraction column.

Although the extraction process is highly efficient in separating the aqueous phase containing hydrogen peroxide from the organic phase containing quinones, solvents, and degradants, some of these organic species remain in the aqueous phase and are generally undesirable to the end user due to their impact on the quality and yield of the final product. Typically, the concentration of these organic impurities ranges from hundreds to tens of mg per kilogram in an aqueous hydrogen peroxide solution with a concentration of 20 to 70% by weight. These organic impurities are usually measured and referred to as Total Organic Carbon (TOC).

The state of the art describes several operations to reduce the organic matter content in the aqueous phase, which can be used alone or in combination with, for example, distillation, gas separation, reverse osmosis, resin adsorption, etc.

EP 0930269 A1 describes a purification process using a reverse osmosis membrane to remove most of the contaminating species from hydrogen peroxide. In this case, the permeate from the reverse osmosis operation has a low TOC content but inherently generates a retentate stream with concentrated TOC, which is undesirable for the end customer and requires additional treatment to reduce the TOC.

In the prior art, a general solution to purify hydrogen peroxide produced by an AO process is the use of an adsorption resin due to the reliability of performance and the low operating cost associated with the possible regeneration of said resin once saturated.

For example, EP 1520839 A1 relates to a hydrogen peroxide purification process using reverse osmosis in combination with an adsorption resin. However, this process does not take into account the regeneration of the used resin, thus generating a high and unwanted amount of resin waste.

US Patent No. 6,896,867 describes a process for producing a purified aqueous hydrogen peroxide solution, in which an adsorption resin is used and regenerated. In this case, the resin is regenerated in the same vessel, resulting in lost time, quality, and a potentially dangerous and undesirable scenario in which the peroxide mixes with the regenerant.

Document CN 208554226 describes a device for purifying electronic-grade hydrogen peroxide, using an adsorption resin in one vessel and regenerated with a regenerant in a separate vessel. This process allows for continuous operation. However, one of the problems with this process is that hydrogen peroxide and/or the regenerant can accumulate in the macroporous resin structure. Furthermore, the transfer of the resin from the purification vessel to the regeneration vessel is performed under vacuum. Vacuum transfer carries the risk of air entering the system, creating an undesirable safety risk scenario in which typical regenerant vapors (e.g., methanol) mix with air in a confined space, thereby causing an explosion. It is well known in the art that mixtures of organic vapors (also called fuel) and air/oxygen (oxidizer) form a combustible mixture that can cause a fire or explosion when located in a confined space. In addition, hydrogen peroxide (oxidant) and regenerant accumulated in the macroporous resin structure can lead to the formation of an explosive mixture in a confined space, and thus an explosion.

In other words, it is difficult to reduce the TOC levels of hydrogen peroxide solutions with the aid of adsorption resins due to the inherent reactivity of hydrogen peroxide when it comes into contact with resins, and the dangerous scenario when hydrogen peroxide comes into contact with organic regenerants. For this reason, not only the productive efficiency of the purification process but also its safe implementation are of utmost importance.

Therefore, the object of the invention was to provide a purification process for hydrogen peroxide solution from an autoxidation (AO) process which overcomes the disadvantages of the processes known in the art, in particular to provide a process for the purification of a hydrogen peroxide solution from an AO process with adsorption resins which has an improved production efficiency, i.e. to provide a hydrogen peroxide solution with a low TOC content, and which can also be carried out safely.

SUMMARY OF THE INVENTION

The present invention relates to a process for the purification of an aqueous hydrogen peroxide solution containing organic impurities, comprising the following steps:

(a) contacting the aqueous hydrogen peroxide solution with an adsorption resin in an adsorption vessel to remove at least part of the organic impurities and obtain a purified aqueous hydrogen peroxide solution that is collected outside the adsorption vessel,

(b) subsequently adding a liquid, preferably demineralized water, to the adsorption vessel such that a suspension of the resin flows out of the adsorption vessel through a first pipe into a regeneration vessel with a pressure, which is higher in the adsorption vessel and in the first pipe than outside the adsorption vessel and the first pipe;

(c) treating the resin in the regeneration vessel with an organic regenerant to obtain a regenerated resin,

(d) returning the regenerated resin through a second pipe to the adsorption vessel using a liquid, preferably demineralized water, with a pressure that is higher in the regeneration vessel and in the second pipe than outside the regeneration vessel and the second pipe.

DETAILED DESCRIPTION OF THE INVENTION

Before describing in detail the purification process of the invention, it should be understood that this invention is not limited to the specific process conditions described herein, as such conditions may of course vary.

It should also be understood that the terminology used herein is not intended to be limiting, as the scope of the present invention will be limited only by the appended claims.

As used here, the singular forms “a,” “an,” and “the” include both singular and plural referents unless the context clearly indicates otherwise. For example, “a compound” means one or more compounds.

The terms “containing,” “contains,” and “contents of,” as used herein, are synonyms for “including,” “includes,” or “comprising,” “comprises,” and are inclusive or open-ended and do not exclude additional members, elements, or steps of the process not mentioned. It will be appreciated that the terms “containing,” “contains,” “comprising,” “comprises,” and “composed of,” as used herein, encompass the terms “consisting of,” “consists,” and “consists of.”

Throughout this application, the term “about” is used to indicate that a value includes the standard deviation of error for the device or method used to determine the value.

As used herein, the term “average” refers to the numerical average unless otherwise indicated.

As used herein, the terms “% by weight,” “% by weight,” “percentage by weight,” or “weight percent” are used interchangeably. The same applies to the terms “% by volume,” “% by vol.”, “percentage by vol.”, or “percentage by volume,” or “% by mol,” “% by mol,” “percentage by mole,” or “percentage by mol.”

The citation of numerical intervals by endpoints includes all whole numbers and, where appropriate, fractions included within that interval (e.g., 1 to 5 may include 1, 2, 3, 4 when referring to, for example, a number of items, and may also include 1.5, 2, 2.75, and 3.80 when referring to, for example, measurements). The citation of endpoints also includes the endpoint values themselves (e.g., 1.0 to 5.0 includes both 1.0 and 5.0). Any numerical interval mentioned here is intended to include all subintervals included within it.

Unless otherwise defined, all terms used in the description of the invention, including technical and scientific terms, have the meaning commonly understood by a person of ordinary skill in the art to which this invention pertains. For further guidance, definitions of terms are included to better understand the teachings of the present invention.

If the description in any patent, patent application, or publication conflicts with the description in this application to the extent that it would make a term unclear, the present description shall prevail.

Various alternatives, embodiments, and variants of the invention are defined in more detail below. Each alternative and embodiment thus defined may be combined with any other alternative and embodiment, and this for each variant unless clearly indicated otherwise or where it is manifestly incompatible when the range of values for a single parameter is disjoint. In particular, any feature indicated as preferred or advantageous may be combined with any other feature or features indicated as preferred or advantageous.

Furthermore, the particular features, structures, or characteristics described herein may be combined in any suitable manner, as would be apparent to one skilled in the art from this description, in one or more embodiments. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features from different embodiments are intended to be within the scope of the invention, and of different embodiments, as would be understood by those in the art.

In order to overcome the disadvantages of the purification processes for the purification of an aqueous hydrogen peroxide solution containing organic impurities as known in the prior art and discussed above, the present invention provides a process comprising the following steps:

(a) contacting the aqueous hydrogen peroxide solution with an adsorption resin in an adsorption vessel to remove at least part of the organic impurities and obtain a purified aqueous hydrogen peroxide solution that is collected outside the adsorption vessel,

(b) subsequently adding a liquid, preferably demineralized water, to the adsorption vessel such that a suspension of the resin flows out of the adsorption vessel through a first pipe into a regeneration vessel with a pressure, which is higher in the adsorption vessel and in the first pipe than outside the adsorption vessel and the first pipe;

(c) treating the resin in the regeneration vessel with an organic regenerant to obtain a regenerated resin,

(d) returning the regenerated resin through a second pipe to the adsorption vessel using a liquid, preferably demineralized water, with a pressure that is higher in the regeneration vessel and in the second pipe than outside the regeneration vessel and the second pipe.

Therefore, the process of the invention comprises four main methodological steps: A purification step, a transfer step, a regeneration step and a recycling step, in which the resin adsorption takes place in one vessel, the resin regeneration takes place in another separate vessel, and the resin is transferred in the form of a suspension with the help of two pipes between both vessels with a pressure, which is higher in the vessels and pipes than outside these vessels and pipes.

According to the invention, it is preferred that the purification vessel and the regeneration vessel have almost similar volumes, more preferably they have the same volume.

A flow diagram is presented in Figure 1, which schematically shows the configuration of the process according to the invention;

Legend:

DMW: demineralized water;

H2O2: hydrogen peroxide input;

H2O2 product: hydrogen peroxide output;

V-1: adsorption vessel;

V-1 effluent: hydrogen peroxide and demineralized water effluent;

MeOH: regenerant inlet;

MeOH used: used regenerant output;

V-2 effluent: regenerant effluent and demineralized water;

A-1: density analysis point at V-1;

A-2: density analysis point at V-2.

The hydrogen peroxide purification vessel (V-1) used in the process of the invention is preferably a column comprising a purification column body, and an upper purification column header and a lower purification column header, which are arranged at the upper and lower ends of the purification column body.

The body of the purification column has an upper part, which is preferably provided with a filter, a membrane and/or a liquid distributor, more preferably the filter, the membrane and/or the liquid distributor is located directly below the upper header of the purification column. The upper purification header preferably has an inlet for demineralized water (DMW of Figure 1) used in the washing step as described below, and an outlet for the purified hydrogen peroxide solution product (H2O2 product of Figure 1). Both the inlet and the outlet are connected by a supply line. In one embodiment of the invention, as shown in Figure 1, the inlet and the outlet of the upper header of the purification column can be the same, and therefore, the upper header of the purification column is only connected to a supply line, which splits outside the vessel (column) into two supply lines, one for supplying the demineralized water and one for supplying the purified hydrogen peroxide product.

Furthermore, the body of the purification column has a lower part, which is preferably provided with a filter, a membrane and/or a liquid distributor, more preferably the filter, the membrane and/or the liquid distributor is located directly above the lower header of the purification column. The lower purification header preferably has an inlet for the hydrogen peroxide solution (H2O2 of Figure 1), which is to be purified, and an outlet for the effluent of the mixture of hydrogen peroxide and demineralized water (Effluent of V-1 of Figure 1) obtained in the washing step as described below. Both the inlet and the outlet are connected by a supply line. In one embodiment of the invention, as shown in Figure 1, the inlet and outlet of the lower header of the purification column may be the same, and therefore the lower header of the purification column is only connected to one supply pipe, which splits outside the vessel (column) into two supply pipes, one for supplying the hydrogen peroxide and one for supplying the effluent of mixture of hydrogen peroxide and demineralized water.

The regeneration vessel (V-2 of Figure 1) is also preferably a column comprising a regeneration column body, and a regeneration column upper header and a regeneration column lower header that are arranged at the upper and lower ends of the regeneration column body.

The regeneration column body has an upper part, which is provided with a filter, a membrane and/or a liquid distributor, more preferably the filter, the membrane and/or the liquid distributor is located directly below the upper header of the regeneration column. The upper header of the regeneration column preferably has an inlet for demineralized water (DMW of Figure 1) used in the washing step as described below, and an inlet for the regenerant (MeOH of Figure 1). Both inlets are connected by a supply line. In one embodiment of the invention, as shown in Figure 1, the upper header of the regeneration column may have only one inlet, and therefore, the upper header of the regeneration column is only connected to a supply line, which splits outside the vessel (column) into two supply lines, one for supplying the demineralized water and one for supplying the regenerant.

Furthermore, the regeneration column has a lower part, which is preferably provided with a filter, a membrane and/or a liquid distributor, more preferably the filter, the membrane and/or the liquid distributor is located directly above the lower header of the regeneration column. The lower regeneration header preferably has an outlet for the used regenerant (used MeOH of Figure 1) and an outlet for the effluent of the mixture of regenerant and demineralized water (Effluent of V-2 of Figure 1) obtained in the washing step as described below. Both outlets are connected by a supply line. In one embodiment of the invention, the lower header of the regeneration column may have only one outlet, as shown in Figure 1, and therefore the lower header of the regeneration column is only connected to a supply line, which splits into two supply lines outside the vessel (column), one for supplying the used regenerant and one for supplying the effluent of the mixture of regenerant and demineralized water.

The filters, membranes and/or liquid distributors present in the containers as described above ensure that the adsorption resin used in the process of the invention remains in the containers for the time necessary to fully carry out the purification and regeneration stage.

Furthermore, according to the invention, the adsorption vessel is provided with a pipe (first pipe) connecting the adsorption vessel to the regeneration vessel. This pipe is preferably connected to the purification column body directly above the filter, membrane, and/or liquid distributor located at the bottom of the purification column body, and preferably connected to the regeneration column body directly below the filter, membrane, and/or liquid distributor located at the top of the regeneration column body.

Furthermore, according to the invention, a second line is used, which also connects both vessels. The second line is preferably connected to the regeneration column body directly above the filter, membrane, and/or liquid distributor located at the bottom of the regeneration column body, and preferably connected to the purification column body directly below the filter, membrane, and/or liquid distributor located at the top of the purification body.

All inlets, outlets and pipes used in the vessel configuration of the invention as described above are equipped with valves to control the flow rate of the liquid streams used in the purification process of the invention.

In a preferred embodiment of the invention, at the end of each stage of the process, a washing step with demineralized water is performed, followed by a concentration analysis, which ensures that no hydrogen peroxide or regenerant is transferred between both containers.

One of the essential features of the present invention lies in the improved ability to remove impurities from an aqueous hydrogen peroxide solution (step (a) of the process of the invention). These contaminants can result, for example, from the process for producing hydrogen peroxide. In the case of the autoxidation (AO) process for producing hydrogen peroxide, the contaminants can be organic hydrocarbon compounds containing functional groups such as alcohols, aldehydes, and carboxylic acids, as well as alkylated aromatics. Diisobutylcarbinol would be a typical alcohol, and tetramethylbenzene would be a typical alkylated aromatic.

The adsorption resin used in the invention is preferably a non-ion exchange adsorbent, in particular a divinylbenzene crosslinked polymeric styrene resin, which is preferably free of washable components such as monomers and polymerization adjuvants. In general, non-ion exchange adsorbents adsorb and release ionic species through hydrophobic and polar interactions, i.e., they have a high affinity for hydrophobic organic substances but a low affinity for hydrophilic materials such as water or H<2>O<2>. The divinylbenzene-crosslinked polymeric styrenic resins, which are preferably used in the process of the invention, can be obtained by suspension polymerization of styrene with divinylbenzene, and have non-ionic functional groups, and their adsorptive properties arise from the macroreticular structure, pore size range, large surface area, and aromatic nature of this surface. Non-ion exchange adsorbents, in particular styrene-divinylbenzene copolymer adsorbents, clearly differ in this respect from cation and anion exchange resins, which due to their functional groups are very sensitive to oxidation and therefore, when used to purify hydrogen peroxide, must be handled with special care (e.g., operating at low temperatures, such as 5 to 10 °C, and low hydrogen peroxide concentration, such as 25 to 35% by weight). In contrast, non-ion exchange adsorbents are stable against oxidation and can be used even at normal room temperatures, such as, for example, 15 to 35 °C, most preferably 20 to 25 °C. They are generally stable at pH 0 to 14 and at temperatures up to 250 °C.

The styrene-divinylbenzene copolymer adsorbents preferably used in the invention have a white or pale yellow color, are bead-shaped, and are insoluble in the treatment medium. Typical properties of these styrene-divinylbenzene copolymer adsorbents are an average particle diameter of 0.5 to 1.3 mm, a water content of 45 to 65%, a relative density of 1.01 to 1.07, and a surface area of 700 to 1300 m2/g, more preferably above 1000 m2/g. These styrene-divinylbenzene copolymers are commercially available, for example sold by Rohm & Haas under the trademark “Amberlite” as XAD-4®, XAD-2®, or XAD-16®, or sold by Sunresin under the trademark “Seplite” as LX-500®. Other commercially available non-ion exchange adsorbents, which can be used in the process of the invention, are acrylic resins such as Diaion HP2MG® and Diaion HP2SS®.

According to the invention, it is preferred that before using the adsorption resin in the purification process of the invention, the resin be washed to free it from production-induced impurities or preservatives, which may degrade or influence the quality of the hydrogen peroxide solution. This may be done by any method known in the art; for example, said washing step may be carried out with the aid of water, preferably demineralized water, and/or lower alcohol, preferably with pure methanol.

By using non-ion exchange adsorbents in the process of the invention, it is possible to purify a hydrogen peroxide solution having a hydrogen peroxide concentration of up to 55% by weight. Preferably, the hydrogen peroxide concentration of the solution to be treated is between 35 and 55% by weight, more preferably between 40 and 53% by weight, even more preferably between 45 and 52% by weight.

Step (a) of the process of the invention is preferably a continuous flow process step in which the hydrogen peroxide solution to be purified is passed through the adsorption vessel. The vessel is preferably a packed bed column with the adsorption resin, in particular when the density of the hydrogen peroxide solution is higher than that of the adsorption resin. The hydrogen peroxide solution is preferably introduced into the vessel at the lower header of the purification column and flows through the vessel (purification column body) preferably at a feed pressure of between 0.5 and 5 barg, more preferably between 0.1 and 3 barg, and preferably at a flow rate of 0.5 to 8 bed volumes (BV) per hour, more preferably 1 to 3 bed volumes per hour, to exit the purification vessel at the upper header of the purification column. The bed volume (BV) depends on the height of the vessel bed (column) and the cross-sectional area of the column body, and is calculated using the following formula:

Bed height (cm) * column cross-sectional area (cm2)

BV (L) = 1000

By carrying out step (a) of the process according to the invention, it is possible to reduce the content of organic impurities, which is typically between 100 and 400 mg/kg, to 25 mg/kg (measured as Total Organic Carbon (TOC), which is determined using the combustion catalytic oxidation method as commonly used in the technical field of the invention and described below in the examples). Preferably, the purified hydrogen peroxide solution product has a TOC content between 25 and 150 mg/kg, more preferably between 40 and 100 mg/kg, most preferably between 50 and 80 mg/kg, measured using the combustion catalytic oxidation method. A further reduction of impurities would be possible by increasing the amount of resin used for a fixed peroxide flow rate, if necessary.

Once the resin has become saturated, i.e. the flow rate of purified hydrogen peroxide solution exiting the adsorption vessel has a constant TOC content as defined above, the flow rate of hydrogen peroxide solution into the vessel is stopped, and demineralized water is preferably passed from the top header of the purification column to the vessel through the vessel (purification column body) until there is no detectable amount of hydrogen peroxide in the vessel; this is typically the case after 80 minutes up to 100 minutes. Preferably, the washing step is carried out at a temperature between 10 and 50 °C, more preferably between 15 and 35 °C. Furthermore, the pressure used in this washing step is preferably from 0.01 bar g to 10 barg, from 0.05 to 8 barg, more preferably from 0.1 to 5 barg. Demineralized water is passed through the packed bed vessel at a flow rate of 2 to 5 bed volumes per hour, preferably 3 to 4 bed volumes per hour.

The amount of hydrogen peroxide present in the vessel can be detected by measuring the density of the effluent mixture containing hydrogen peroxide and demineralized water, which exits the vessel at the bottom header of the purification column (see Figure 1, A-1). It is common knowledge that different materials have different densities, and that the density of a mixture of components is the result of the combination of different densities of these components; for example, at 20 °C, methanol has a density of 791.4 kg/m3; water has a density of 998.2 kg/m3; and 100% hydrogen peroxide has a density of 1448.0 kg/m3.

If the measured density of the effluent mixture containing hydrogen peroxide and demineralized water exiting the vessel through the lower header of the purification column corresponds to the density of the demineralized water, i.e., the density is preferably 998.2 kg/m3 ± 0.1 kg/m3 at 20 °C, the "mixture" exiting the vessel no longer contains hydrogen peroxide. Consequently, no hydrogen peroxide remains in the vessel.

At this point, the adsorption resin with demineralized water is transferred from the adsorption vessel to the regeneration vessel through a first line, which connects the two vessels as described above. This transfer according to step (b) of the process of the invention is carried out under a pressure that is higher inside the adsorption vessel and the first line than outside the adsorption vessel and the first line, i.e., the transfer of the resin in suspension form is carried out under positive pressure, preferably at a pressure higher than ambient pressure, i.e., higher than 1.01 bara. According to the invention, the pressure is preferably between 1.5 and 3 bara. The pressure is created using a flow rate of demineralized water introduced into the adsorption vessel, which is between 2 and 6 bed volumes per hour, more preferably between 3 and 5 bed volumes per hour.

The use of positive pressure prevents air from entering the system. Furthermore, due to the washing step of the adsorption vessel as described above, hydrogen peroxide is not undesirably transferred to the regeneration vessel.

It is a known fact that adsorption resins can generally be regenerated. Typical regenerants, which are also used in the regeneration process step of the invention (process step (c)), are lower alcohols such as methanol, ethanol, or isopropanol. In a preferred embodiment of the invention, methanol is used as the regenerant.

Once the adsorption resin with demineralized water has been completely transferred to the second vessel, the resin, which is preferably packed in the bed in the regeneration column body, is regenerated with the regenerant passing through the vessel (regeneration column body), preferably from the upper header of the regeneration column to the lower header of the regeneration column. The amount of organic regenerant used in step (c) is at least 1 bed volume, preferably at least 1.5 bed volumes.

According to the invention, it is preferred that the regenerant be used in the form of an aqueous solution. This solution is passed from the top header of the regeneration column to the bottom header of the regeneration column at a flow rate of 1 to 4 bed volumes per hour, preferably 2 to 3 bed volumes per hour. The regeneration process step is carried out for at least 60 minutes, preferably at least 90 minutes.

The regenerant can be reused after use by separating the impurities using a suitable technique such as distillation. Therefore, the used regenerant is collected for distillation and reuse in one or more consecutive cycles (see used MeOH in Figure 1).

Once the adsorption resin has been regenerated, i.e. is essentially free of adsorbed organic, which is usually the case after 80 minutes, preferably after 60 minutes, the introduction of regenerant into the regeneration vessel is stopped and demineralized water is passed through the vessel (regeneration column body) downwards until the density of the mixture is that of demineralized water, to ensure that no regenerant remains inside the vessel, i.e. the density of the “mixture” is at 20 °C 998.2 kg/m3 ± 0.1 kg/m3 and is measured after the mixture containing the regenerant effluent and demineralized water (used MeOH from Figure 1) has left the regeneration vessel at the lower head of the regeneration column (see Figure 1, A-2). The washing step is preferably carried out at a temperature of between 10 and 50 °C, more preferably between 15 and 35 °C. Furthermore, the pressure used in this washing step is preferably from 0.01 barg to 10 barg, from 0.05 to 8 barg, more preferably from 0.1 to 5 barg.

In this step of the process of the invention, the regenerated adsorption resin is transferred with demineralized water to the first vessel through the second line, which further connects the two vessels as described above. The resin is then ready to be brought back into contact with hydrogen peroxide. This transfer step (step (d) of the process of the invention) is carried out under a pressure that is higher inside the regeneration vessel and the second line than outside the regeneration vessel and the second line, i.e., the transfer of the resin in the form of a suspension is carried out under positive pressure, preferably at a pressure higher than ambient pressure, i.e., higher than 1.01 bara, preferably between 1.5 and 3 bara. The pressure is created using a flow rate of demineralized water introduced into the regeneration vessel, which is between 2 and 6 bed volumes per hour, more preferably between 3 and 5 bed volumes per hour.

The process of the invention can be carried out in batch mode or in continuous mode. If the process is carried out in continuous mode, at least two adsorption vessel and regeneration vessel assemblies as described above are used to carry out the process; that is, the process of the invention is carried out in a staggered manner in these two adsorption vessel and regeneration vessel assemblies to ensure a continuous process.

The present invention is further illustrated by the following examples. It should be understood that the following examples are for illustrative purposes only and are not intended to limit the present invention to the same.

EXAMPLES

EXAMPLE 1

An aqueous hydrogen peroxide solution at a concentration of 50% by weight and 295 mg TOC/kg was continuously fed into a vessel containing 268 g of styrene-divinylbenzene polymer resin at 20 °C. The resin used was Seplite LX-500® from Sunresin. At a feed pressure of 0.2 barg, a flow rate of 1.7 L/h (or 4 bed volumes per hour, 4 BV/h) was passed through the packed bed upwards until the resin was saturated and reached an average TOC value of 67 mg/kg. A total of 66.6 kg of purified hydrogen peroxide was collected.

Subsequently, a flow rate of 4BV of demineralized water was passed downwards through the packed bed for 80 minutes, to eliminate hydrogen peroxide retention, until the output stream density measurement was that of demineralized water.

The resin is then transferred to a vessel of similar volume via a connected pipeline using a flow rate of 4 BV/h of demineralized water until no resin remains in the first vessel.

Subsequently, a flow rate of 2 BV/h of methanol was passed downwards through the packed bed for 60 minutes to regenerate the resin.

Subsequently, a flow rate of 4BV of demineralized water was passed downwards through the packed bed for 90 minutes, to eliminate menthol retention, until the density measurement of the outlet stream was that of demineralized water.

The resin is then transferred to the first vessel via a connected pipeline using a flow rate of 4 BV/h of demineralized water until no resin remains in the outlet vessel.

The mixture of methanol, organic impurities, and demineralized water was collected for methanol reuse. A batch distillation system consisting of 15 theoretical plates was used to separate the mixture, yielding methanol with a purity of 99% by weight, which can be reused in the next resin regeneration.

EXAMPLES 2-20

Examples 2-20 were carried out in the same manner as Example 1, i.e., the complete cycle was repeated 19 times. All examples show similar performances:

Table 1

Table 2

The TOC content was measured using the catalytic combustion oxidation method, as commonly used in the technical field of the invention. In this method, the samples used to determine the TOC content are heated to 680°C in an oxygen-rich environment inside TC combustion tubes filled with a platinum catalyst to decompose organic carbon impurities present in the sample and convert them into carbon dioxide. The carbon dioxide generated is detected using an infrared gas analyzer. The total carbon (TC) concentration in the sample is obtained by comparison with a calibration curve.

Claims (15)

1. A process for the purification of an aqueous hydrogen peroxide solution containing organic impurities, comprising the following steps: (a) contacting the aqueous hydrogen peroxide solution with an adsorption resin in an adsorption vessel to remove at least part of the organic impurities and obtain a purified aqueous hydrogen peroxide solution that is collected outside the adsorption vessel, (b) subsequently adding a liquid, preferably demineralized water, to the adsorption vessel such that a suspension of the resin flows out of the adsorption vessel through a first line into a regeneration vessel with a pressure that is higher in the adsorption vessel and in the first line than outside the adsorption vessel and the first line; (c) treating the resin in the regeneration vessel with an organic regenerant to obtain a regenerated resin, (d) returning the regenerated resin through a second pipe to the adsorption vessel using a liquid, preferably demineralized water, with a pressure that is higher in the regeneration vessel and in the second pipe than outside the regeneration vessel and the second pipe. 2. The method of claim 1, wherein, after step (a) and/or after step (c), the container(s) used therein are washed with demineralized water until no detectable amount of hydrogen peroxide and/or regenerant remains in the container. 3. The method of claim 2, wherein the presence of hydrogen peroxide in the container is measured by analyzing the density of the wash liquid exiting the container. 4. The method of claim 2 or 3, wherein the washing is carried out at a temperature of 10 to 50 °C and a pressure of 0.01 barg to 10 barg. 5. The process of any one of the preceding claims, wherein the aqueous hydrogen peroxide solution, before its purification, contains organic impurities in an amount of 100 to 400 mg/kg, measured using the catalytic combustion oxidation method. 6. The method of any one of the preceding claims, wherein the amount of organic impurities in the purified aqueous hydrogen peroxide solution is 25 to 150 mg/kg. 7. The process of any one of the preceding claims, wherein the organic impurities are chosen from organic hydrocarbon compounds containing functional groups such as alcohols, aldehydes, carboxylic acids, and alkylated aromatics, in particular diisobutylcarbinol and/or tetramethylbenzene. 8. The method of any one of the preceding claims, wherein step (a) is carried out at a temperature of 15 to 35 °C, most preferably 20 to 25 °C. 9. The method of any one of the preceding claims, wherein the amount of hydrogen peroxide in the aqueous hydrogen peroxide solution is 40 to 55% by weight. 10. The method of any one of the preceding claims, wherein the adsorption resin is chosen from non-ion exchange adsorbents, preferably polymeric styrene resins crosslinked with divinylbenzene. 11. The method of any one of the preceding claims, wherein the pressure used in step (b) is 0.1 to 1 barg, for example 0.5 barg. 12. The process of any one of the preceding claims, wherein the regenerant used in step (c) is chosen from alcohols such as methanol, ethanol, isopropanol, or combinations thereof. 13. The method of any one of the preceding claims, wherein the organic regenerant is used in step (c) in an amount of at least 1 bed volume. 14. The process of any one of the preceding claims, wherein the used regenerant is collected for distillation and optional reuse in a consecutive purification in one or more cycles. 15. The process of any one of the preceding claims, wherein the process is carried out in a continuous mode using at least two sets of adsorption vessel and regeneration vessel to carry out the process.